The fog rolled in over the mountains in Krasnaya Polyana on Sunday night and was still shrouding some of the Olympic skiing venues in a cloud-like mist by late Monday afternoon. That prompted organizers to call off the men's biathlon mass-start race and men's snowboardcross almost simultaneously.
The rescheduling didn't seem to be a major concern for the athletes, though.
"This is standard for snowboarding and ski events. Mother Nature doesn't always cooperate," American snowboardcross rider Nate Holland said.
The biathlon race had already been pushed back from Sunday evening to Monday morning, and was then postponed to mid-afternoon before being called off for another day. It will now be held Tuesday at 2:30 p.m., organizers said.
"Well, I am going to sleep again," double Olympic champion Martin Fourcade tweeted in French after the race was postponed. "We'll see each other tomorrow!"
The fog eventually subsided and the women's mass-start race went ahead at its scheduled 7 p.m. start.
At the Rosa Khutor Extreme Park, the snowboardcross was also first delayed then postponed. Organizers first canceled the seeding runs for the event, then pushed back the elimination races before calling it a day. The elimination races will now start at 10:30 a.m. Tuesday, with the seeding runs scrapped.
The Alpine schedule wasn't affected Monday, but the women's giant slalom on Tuesday was pushed forward by 90 minutes to avoid problems. Rain and snow is forecast to begin falling on Tuesday morning and continue through the afternoon. The first run will now begin at 9.30 a.m. and the second at 1 p.m.
Jessica Lindell-Vikarby of Sweden, one of the favorites in the GS, said it would have been impossible to have the event on Monday.
"When it's this thick you cannot race," Lindell-Vikarby said. "It has to be more open, for sure."
The ski jumping venue is at a lower altitude and was not shrouded in the thick fog. A training round for Nordic combined athletes was held without disruptions, and the ski jump team event was also expected to go ahead as scheduled on Monday.
The fog is causing a new challenge for the athletes following days of sunshine and unseasonably warm weather. At the Laura Cross Country Ski and Biathlon Center, the high temperatures toward the end of last week had softened the snow and led to some cross-country skiers cutting off the sleeves on their suits.
In biathlon, fog is an even bigger problem because it limits the visibility on the shooting range.
"You have to be able to hit the targets," said Jerry Kokesh, the editor of the International Biathlon Union's official website, adding that the course becomes more dangerous as well. "Uphills are not a problem, but downhills are. ... That can be a serious safety concern."
The first week of the games went by without any major disruptions to the schedule before Sunday's biathlon race was postponed, despite concerns going into the Olympics about the warm climate in Sochi. IOC spokesman Mark Adams said every Winter Olympics normally faces some rescheduling because of the weather, and that Sochi has been relatively unaffected.
"In terms of what's going on there, I think it's actually quite ironic that the biggest issue we've had so far is due to winter fog," Adams said. "Winter sports is very unpredictable. It's a very dynamic field of play. At present, the conditions are good and we are continuing. We haven't had any major complaints up there."
Certainly not from Holland, the snowboarder, who said it was better to wait another day than to compete in poor conditions.
"It's the Olympics, we want to have the best rider win and not have anything screwy," Holland said. "So we'll be back tomorrow and let her roll from there. It's time to drop the hammer and the sickle on this course."
AP Sports Writers Will Graves, Jon Krawczynski, Andrew Dampf and Pat Graham contributed to this report.